If you are willing to dedicate the time and space, I think Black & Whaite Argentinian tegus are the best reptile one could keep...
I have an '08 Arg B&W male purchased from Vanyard (Bobby Hill) that I simply could not be happier with. I got it as a 9" hatchling and now it's a 50", 12 lb big sweetie.
They require a very large enclosure. Mine is in an 8' x 3' enclosure (inside cage) and in the summer months he lives on a 6' x 12' deck/balcony. With that experience, I feel an 8' x 3' would be the minimum acceptible size for a male (males get larger than females).
I have a few local friends that have adult Savs. They each argued that Savs can become "puppy tame", but once they met my adult Tegu, they each admitted they do not believe a Sav could ever be as tame as my Tegu is.
I've done nothing special to raise my Tegu. Simply gave it a large enough enclosure, frequent kind attention and a healthy diet. He has been to "Reptile Days" at a local college and did perfect. He visits local Pet Shops with me frequently (as weather allows) and does marvelous. He is completely tolerant of both adults and children petting, poking and pulling at him.
He eats a wide variety of processed meats that can easily (and inexpensively) be purchased at the local grocery store, or he will eagerly eat rats, mice, chicks, etc.
Between a Sav and a Tegu... I'd strongly suggest the Arg B&W Tegu...
But the pythons and Tegus will have both very different enclosure requirements as well as very different care needs. The snakes require far less "hands on" time, can stay in a much smaller enclosure... but on the down side they will require whole prey which is a bit more complicated than ground turkey, beef liver, etc, etc.